Would your kids know precisely what to do, if an active shooter entered their school? It's a question a lot of parents are asking more and more, especially since the mass shooting in Florida this week.

Eyewitness News spent Friday morning at Garden City High School in Long Island, with school administrators and Don Flynn, a former NYPD Detective, who now runs a security consulting firm for more than a dozen schools. And some of the protocols are changing.

"There just can't be one option. There has to be multiple," Flynn said.

The first safety tip: barricade the classroom door. Most classroom doors now lock from the inside while closed.

Next, hide, preferably under something. However, security experts are starting to advise students, at least those in high school, against huddling together in one corner.

"We're trying to emphasize -- spread out a little bit," Flynn said.

It's because all too often, they are seeing shooters aiming right at a whole group.

"If we have to get to that last resort as far as trying to fight, it also helps," he added.

It doesn't matter that Garden City High School is nowhere near Parkland, Florida. The fear resonates.

"It just makes you so nervous, that gun violence doesn't discriminate," Garden City High School senior Tommy Flanagan said. "This could happen here."

The school had a previously scheduled lockdown that was supposed to take place on Thursday, and it was supposed to be unannounced. But given what happened this week, it would have been too traumatic. So Friday morning, they informed the students of a drill.

Experts say you should also know precisely which window is a rescue window inside your classroom. It is usually marked. And while it's hard to stay off your cellphone, keep in mind.it could be a hazard. In Florida, some students took to social media, which is not advised.

"They thought they were saying goodbye to loved ones," Flynn said. "So there is that aspect of it. But in the best case scenario, silence the phones."

Garden City is one of the few communities where school security cameras are now linked to the local police department.

"We get an incident, they turn on the cameras. We know if there's an intruder, where the intruder is, how many intruders exactly what's going on," Acting Superintendent Dr. Alan Groveman said.

Experts believe that on average, students and teachers will only be on their own for the first three to four minutes of any crisis. But what they do before help arrives, can mean life or death.